1. Technical Field
The present invention relates to an armature core, motor using the armature core, and axial gap electrical rotating machine (axial gap motor) having gaps in the axial direction.
2. Description of the Related Art
In recent years, electrical rotating machines with high efficiency and low cost are in demand in view of fuel shortage, environmental contamination, and economy. Amorphous metal is considered to be used for such electrical rotational machines. Being materials excellent in magnetic and mechanical properties including low loss, high magnetic permeability, high strength and rust resistance, amorphous metals are expected for motor cores in application to high efficiency and low cost of a motor.
A commonly used amorphous metal is in a thin and continuous ribbon form having a constant width. With regard to manufacturing methods of a core from an amorphous metal in a ribbon form, related arts can be roughly categorized into three methods. A first method uses a lamination of wound ring forms of the amorphous metal as a core. For example, in Patent Document 1, an example is described where a magnetic body made by winding a continuous amorphous metallic ribbon, cutting it, and then forming is used as a core. Herein, because the wound core is used as it is, a loop circuit is formed with respect to current flowing, which causes a large eddy current loss.
Further, there is nothing that protects the outer side of a core, which makes it difficult to arrange winding wires.
Still further, as a member for insertion to be applied between cores for fixing the cores is necessary, there is a problem of a complicated manufacturing process.
As a second method, a part cut from a body formed by winding amorphous metal is used as a core. For example, in Patent Document 2, a core made by winding an amorphous thin body is held at the outer circumference thereof by a shape maintaining material, such as a silicon steel plate, and attached to a forming jig for forming. In this state, heat treatment and annealing treatment are performed. Thereafter, the silicon steel plate is removed, and then, cut and after cutting, an adhesive agent is coated on the cut surface. By this method, because not all of the winding core can be cut, there is a problem of a low utilization ratio, and it is also highly possible that rust is caused through cutting. Further, there is a problem that the shape and dimensions of a core cannot be easily designed.
As a third method, a core is manufactured by coating an adhesive agent on small pieces of amorphous metal, laminating the plurality of amorphous small pieces, and heat-press-bonding the lamination. As an example, a technology for manufacturing amorphous lamination material is described in Patent Document 3. However, coating an adhesive agent causes a problem of lowering the volume ratio of the core.
The basic structure of a permanent-magnet-synchronization electrical rotating machine is configured with a soft magnetic material, coils, and permanent magnets. The losses of such an electrical rotating machine can be roughly categorized into iron loss and copper loss. The iron loss is determined by the properties of a soft magnetic material. The copper loss is determined by the resistance value of the coil, in other words, by the volume ratio, wherein the more compact the structure of the winding is, the smaller the loss is. A method of increasing the efficiency can be attained by a design of the shape, dimensions and the like of an electrical rotating machine, which makes these losses to be low, however, a change in the properties of the material also contributes to high efficiency.
Employment of an axial gap electrical rotating machine is considered to be one of methods for decreasing the loss of a flat electrical rotating machine structure. A stator used for a radial electrical rotating machine which is flat and thin in the axis direction of the rotor shaft is in most cases given with a structure having a winding wire around a core part that is formed by punching electromagnetic steel plates and laminating the punched plates along the axial direction of a rotor shaft. However, because the ratio of the coil end portion of the coil becomes large with respect to the core part facing the rotor and being effective for torque output, the coil resistance value becomes large, which increases the copper loss. Accordingly, for the structure of flat electrical rotating machines, axial types in which the surfaces, of the core portions, contributable to the torque output and facing the rotors are arranged along the axial direction of the rotor shaft are effective for reducing the copper loss. Further, for the core portions, it is desirable to adopt a material with a high magnetic permeability and low iron loss in order to reduce the iron loss.
One basic structure of an axial gap electrical rotating machine is disclosed by Patent Document 4. Having a teeth portion and yoke portion, this structure has facing surfaces contributable to torque output only on one side with respect to the rotor axis direction. Further, because a magnetic flux flows from the teeth portion to the yoke portion in this structure, it is necessary to use a soft magnetic material for which a consideration is made so that a magnetic flux flows in the yoke portion three dimensionally. In order to satisfy these requirements, it is necessary to use a material, such as a powder magnetic core, whose magnetic characteristics has three dimensional isotropy, however, such a material has lower magnetic permeability and larger iron loss than commonly used silicon steel plates, causing a problem of difficulty with downsizing in obtaining an electrical rotating machine with a high output.
As a solution for solving the above-described problems, there is proposed a technology for an electric rotating machine described in Patent Document 5. With the electrical rotating machine described in Patent Document 2, an example is disclosed where a stator is provided with two surfaces in the axis direction of the rotor shaft, the surfaces facing rotors, and cores are structured with silicon steel plates. A method is disclosed in which, after a wire is wound around cores, and the cores are fixed by molding with a resin member to form a stator.